Subchronic mild noise stress increases HRP permeability in rat small intestine in vitro

Recently we reported an increased trans- and paracellular protein permeabil ity in rat small intestine after acute cold restraint stress. In the presen t study, we applied randomized 95- or 105-dB white noise pulses during 45 m in/h, 12 h/day, duration 8 days, as a milder, but more chronic stressor to male rats. At 8 days before the noise experiments, 50% of the animals were cannulated in the vena cava for blood sampling during the experimental peri od. The other 50% of the animals were sacrificed at Day 9, segments of ileu m were mounted in Ussing chambers and perfused at 37 degreesC. Horseradish peroxidase (HRP) was added mucosally, serosal appearance was detected enzym atically and tissues were fixed for electron microscopy. In the animals exp osed to 95-dB noise, plasma corticosterone levels were enhanced twofold com pared to controls, and ileal HRP flux was enhanced twofold. Electron microg raphs of tissue from stressed or control animals showed no detectable parac ellular staining of HRP. Quantification of HRP-containing endosomes in ente rocytes revealed a twofold increase in endosome number in the animals expos ed to 95-db noise indicating that the increased HRP permeability was primar ily due to increased endocytosis. In contrast to the animals exposed to 95- dB noise, rats exposed to 105-dB noise showed no increase in corticosterone levels and ileal HRP fluxes were not significantly different from controls . We conclude that mild subchronic noise stress may cause a decrease in int estinal barrier function by increased transcytosis of luminal antigens. (C) 2001 Elsevier Science Inc. All rights reserved.